tach drive HEI
12-22-2001, 01:09 AM
#1
Racer
Thread Starter
tach drive HEI
I know you can buy these, but they are quite expensive. Has anyone successfully taken a tach drive distributor, cut off the top and mated it to the top section of an HEI distributor? Seems like you should be able to do this with a good lathe (which I have) and some patience. I have a good HEI distributor, and when I get hold of a tach drive distributor I am going to give it a shot. Any success stories and how you did it?
12-22-2001, 01:27 AM
#2
Safety Car
Re: tach drive HEI (john73bb)
Never heard of that idea before. I suppose it "could" be done. Definatly not worth the trouble. Ive had good luck with converting my stock 73 tac drive dist to the Pertronix electronic trigger. The stock 73 points style dist is much smaller and allows the coil to remain in the stock location as well. I would recomend converting your stock dist to one of these trigger types. I run a 50k volt stock size canister coil with my setup. 50k is plenty hot. Setting up the advance curve is important to get best performance from your ignition too.
Wait a minute, ont the coil location I just realized the HEI coil is in the cap. At first I didnt realize you were running a computor controlled setup.
[Modified by Jvette73, 11:31 PM 12/21/2001]
Wait a minute, ont the coil location I just realized the HEI coil is in the cap. At first I didnt realize you were running a computor controlled setup.
[Modified by Jvette73, 11:31 PM 12/21/2001]
12-22-2001, 01:35 AM
#3
Racer
Thread Starter
Re: tach drive HEI (Jvette73)
I have the pertronix ignition and a high voltage coil now. If I convert to HEI, I can control the spark with the ECU I am installing. It is out of a 90 chevy van, and will control the ignition modules that have the computer connection. Hence, the desire to use an HEI, but keep my tach drive. I could get a later model electronic tach too, but I kind of like the "novelty" if you will of having the mechanical tach.
12-22-2001, 01:58 AM
#4
Safety Car
Re: tach drive HEI (john73bb)
I've the same problem with my planned EFI conversion. I found this a while back, but I would modify it a bit. I wouldn't use JBweld, only "real" welding. I may go with the computer controlled MSD and an electronic tach if the budget allows...
[B]I can't take any credit for this, the procedure was posted by a guy on another board. I'm definitely adding this to my list of things to try! Modern electronic ignition with a totally stock look and cheap spare parts available at your local auto parts store.
I have created my own Small Body HEI using a Point Distributor (PD) and parts from a Junk HEI. The conversion was somewhat time consuming but not all that difficult to do. If you like to “tinker” and you have some spare time you might want to try it yourself.
It is best to start with a PD that is in good condition. If the bushings or shaft are worn you may want to get another core to work with. You can replace the bushings but it is simpler to just start with a PD that is in good condition. The PD needs to be one that fits your motor. It does not matter what the HEI is out of, you will only be using part of one part and the electronics (recommend you buy new electronic parts). You can use a Junk HEI. I have several that have broken housings and the conversion parts work fine. You should be able to get an HEI with a broken housing for next to nothing.
The HEI has a Pickup/Pickup Coil Assembly (PCA), a Reluctor (may also be called a Trigger Wheel, Timer Core, Rotating Pole Piece or Armature) a Capacitor and a Module. You need to transfer these parts to the points distributor. The Module and Capacitor are optional. You do not need to use a Module or Capacitor if you use an MSD or similar ignition.
The only tools I used were a Drill Press, Bench Grinder, Hacksaw, File, Sandpaper and common tools like screwdrivers and wrenches. You need to do some cutting to do this the way I did. That is where the Drill Press, Hacksaw, File and Grinder come into use.
You first remove all the parts (except for the bushings) from the distributors. I put all the parts on two fairly large towels to try to keep from getting the parts mixed up. It is helpful to have a spare PD and HEI handy so you can see how they are assembled.
My first modification was to install the PCA. It sets in the same location as the points plate. However, it is slightly taller than the points plate and the retaining clip will not fit into the groove without some modification. I cut down the PD Housing to get the needed clearance. The way I performed this modification was to put the Shaft from the HEI (you won’t use it, so it won’t matter if the HEI Shaft is damaged.) into the PD Housing upside down. Use electrical tape (holds well and easy to remove) to lock the Shaft from turning in the Housing and put it in the Drill Press. Use the Drill Press and File like a Lathe to cut down the Housing enough to let the retaining clip fit into place on top of the PCA. When you cut down the housing you are no longer able to install the Plastic Grease Seal. This does not concern me as I don’t think there should be any dirt in this area to cause problems and to date (>9 months) no grease has come out.
You also need to modify the part of the PCA that attaches to the Vacuum Advance Canister (VAC). This was fairly easy to do. I took two pairs of needle nose pliers and bent the arm into an L shape. You want to get this in exactly the right position so it does not cause the VAC or PCA to bind.
The next step is to cut the Reluctor (from HEI) off and cut off the points cam (from PD.) I used the Drill Press and Hacksaw again for this. Be sure to use the HEI Shaft for the cutting project as you will probably cut too far and you do not want to ruin your PD Shaft. I cut the parts long and made final adjustments with the bench grinder. I did this by trial and error till I had the clearance (.008”) I wanted at the Dist. Gear with one shim in place.
The last step in the modifications is to “weld” the Reluctor to the remaining part of the points cam. I initially tried to use a MIG Welder to do this but found I could not easily keep the parts lined up to do the welding and I was concerned I might weld the parts to the shaft. In my final assembly I used JB Weld. It does not appear that this area is highly stressed and you can apply the JB Weld to a large surface area so I think it should be plenty strong. I did this last Winter (> 9 months ago) and it has held up fine.
The way my Distributor is currently set up I have a Rotor Phasing Problem (the rotor tip is not pointing directly at the cap terminal when the spark fires) I assumed that the Reluctor and PCA “Star Points” should point at each other when the rotor tip is pointed at the cap terminal. That is how I set mine up and apparently it is not correct. I have been able to deal with the phasing problem by reversing the PCA leads to my MSD 6AL and by using an MSD Cap Adapt (has Adjustable Rotor Phasing) but I plan to try to correct the problem by cutting off the JB Weld and repositioning the Reluctor. Since it has been working well I decided to wait for cold weather before attempting to correct this. I will look at a stock HEI and see where the “Star Points” are at when the rotor tip and cap terminal are lined up and try to duplicate that. Hopefully it will be close.
[B]I can't take any credit for this, the procedure was posted by a guy on another board. I'm definitely adding this to my list of things to try! Modern electronic ignition with a totally stock look and cheap spare parts available at your local auto parts store.
I have created my own Small Body HEI using a Point Distributor (PD) and parts from a Junk HEI. The conversion was somewhat time consuming but not all that difficult to do. If you like to “tinker” and you have some spare time you might want to try it yourself.
It is best to start with a PD that is in good condition. If the bushings or shaft are worn you may want to get another core to work with. You can replace the bushings but it is simpler to just start with a PD that is in good condition. The PD needs to be one that fits your motor. It does not matter what the HEI is out of, you will only be using part of one part and the electronics (recommend you buy new electronic parts). You can use a Junk HEI. I have several that have broken housings and the conversion parts work fine. You should be able to get an HEI with a broken housing for next to nothing.
The HEI has a Pickup/Pickup Coil Assembly (PCA), a Reluctor (may also be called a Trigger Wheel, Timer Core, Rotating Pole Piece or Armature) a Capacitor and a Module. You need to transfer these parts to the points distributor. The Module and Capacitor are optional. You do not need to use a Module or Capacitor if you use an MSD or similar ignition.
The only tools I used were a Drill Press, Bench Grinder, Hacksaw, File, Sandpaper and common tools like screwdrivers and wrenches. You need to do some cutting to do this the way I did. That is where the Drill Press, Hacksaw, File and Grinder come into use.
You first remove all the parts (except for the bushings) from the distributors. I put all the parts on two fairly large towels to try to keep from getting the parts mixed up. It is helpful to have a spare PD and HEI handy so you can see how they are assembled.
My first modification was to install the PCA. It sets in the same location as the points plate. However, it is slightly taller than the points plate and the retaining clip will not fit into the groove without some modification. I cut down the PD Housing to get the needed clearance. The way I performed this modification was to put the Shaft from the HEI (you won’t use it, so it won’t matter if the HEI Shaft is damaged.) into the PD Housing upside down. Use electrical tape (holds well and easy to remove) to lock the Shaft from turning in the Housing and put it in the Drill Press. Use the Drill Press and File like a Lathe to cut down the Housing enough to let the retaining clip fit into place on top of the PCA. When you cut down the housing you are no longer able to install the Plastic Grease Seal. This does not concern me as I don’t think there should be any dirt in this area to cause problems and to date (>9 months) no grease has come out.
You also need to modify the part of the PCA that attaches to the Vacuum Advance Canister (VAC). This was fairly easy to do. I took two pairs of needle nose pliers and bent the arm into an L shape. You want to get this in exactly the right position so it does not cause the VAC or PCA to bind.
The next step is to cut the Reluctor (from HEI) off and cut off the points cam (from PD.) I used the Drill Press and Hacksaw again for this. Be sure to use the HEI Shaft for the cutting project as you will probably cut too far and you do not want to ruin your PD Shaft. I cut the parts long and made final adjustments with the bench grinder. I did this by trial and error till I had the clearance (.008”) I wanted at the Dist. Gear with one shim in place.
The last step in the modifications is to “weld” the Reluctor to the remaining part of the points cam. I initially tried to use a MIG Welder to do this but found I could not easily keep the parts lined up to do the welding and I was concerned I might weld the parts to the shaft. In my final assembly I used JB Weld. It does not appear that this area is highly stressed and you can apply the JB Weld to a large surface area so I think it should be plenty strong. I did this last Winter (> 9 months ago) and it has held up fine.
The way my Distributor is currently set up I have a Rotor Phasing Problem (the rotor tip is not pointing directly at the cap terminal when the spark fires) I assumed that the Reluctor and PCA “Star Points” should point at each other when the rotor tip is pointed at the cap terminal. That is how I set mine up and apparently it is not correct. I have been able to deal with the phasing problem by reversing the PCA leads to my MSD 6AL and by using an MSD Cap Adapt (has Adjustable Rotor Phasing) but I plan to try to correct the problem by cutting off the JB Weld and repositioning the Reluctor. Since it has been working well I decided to wait for cold weather before attempting to correct this. I will look at a stock HEI and see where the “Star Points” are at when the rotor tip and cap terminal are lined up and try to duplicate that. Hopefully it will be close.
12-22-2001, 02:05 AM
#5
Racer
Thread Starter
Re: tach drive HEI (Flareside)
Yes, I remember seeing that post. This retains stock look, which is nice, but I'm not that concerned about stock look. With this conversion, you have to mount the module external to the cap since it won't fit inside. This might actually be OK, thinking about it. Just mount it to a nice heat sink with some heat sink compound and run the reluctor wires into the cap.
If I can't see a good way to do it with the lathe and welder I may try this. It would still be nice to have a HEI top and a tach drive bottom on the distributor.
If I can't see a good way to do it with the lathe and welder I may try this. It would still be nice to have a HEI top and a tach drive bottom on the distributor.
12-22-2001, 02:14 AM
#6
Safety Car
Re: tach drive HEI (john73bb)
Not all OEM HEIs use a cap-in-coil. The later computer controlled units have an external coil and two connectors at the distributor. Just FYI..
Somebody makes the distributor you're talking about, an old style HEI with a tach drive. It's in the Eckler's catalog. I think they had both types (mechanical and computer)
[Modified by Flareside, 11:33 PM 12/28/2001]
Somebody makes the distributor you're talking about, an old style HEI with a tach drive. It's in the Eckler's catalog. I think they had both types (mechanical and computer)
[Modified by Flareside, 11:33 PM 12/28/2001]
12-22-2001, 10:15 AM
#9
Le Mans Master
Re: tach drive HEI (Alwyn678)
hey john if you are gone to mount the module outside look at a later caprice or vette or camaro Lt-1 they have the module mounted on a nice heatsink mounted on the drivers side head up front.just fyi
12-22-2001, 12:34 PM
#10
Drifting
Member Since: Oct 2001
Location: Halifax, Nova Scotia, Canada
Posts: 1,865
Received 825 Likes
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242 Posts
Re: tach drive HEI (john73bb)
Another option....
If you want to use HEI and retain your stock distributor, with "NO"
modification to the distributor, then use the GM stock T.I. distributor parts. http://www.tispecialty.com/products/distributors.htm
They bolt right in with no modifications.
(Well,, only modification would be to your wallet)
Then use the external HEI components (as mentioned above) and complete
the installation.
Barry
If you want to use HEI and retain your stock distributor, with "NO"
modification to the distributor, then use the GM stock T.I. distributor parts. http://www.tispecialty.com/products/distributors.htm
They bolt right in with no modifications.
(Well,, only modification would be to your wallet)
Then use the external HEI components (as mentioned above) and complete
the installation.
Barry
12-22-2001, 12:56 PM
#11
Racer
Thread Starter
Re: tach drive HEI (Barry's70LT1)
Barry,
That's a great idea. I remember seeing quite a few of these transistor ignition distributors at a swap meet last year for not all that much money. They have the pickup and rotor and everything I need. I might give that a shot. I am planning on going to the same swap meet in February again, I will see what I can find.
That's a great idea. I remember seeing quite a few of these transistor ignition distributors at a swap meet last year for not all that much money. They have the pickup and rotor and everything I need. I might give that a shot. I am planning on going to the same swap meet in February again, I will see what I can find.
